Delete comments when TC and TE are removed. Closes #1028

we do this with a pre-delete signal b/c the object_pk field
isn't a FK relationship but rather an integer field so we can't
rely on a cascading delete!

tcms/signals.py

@@ -1,6 +1,6 @@
 # pylint: disable=unused-argument
 """
-Defines custom signals sent throught out Kiwi TCMS. You can connect your own
+Defines custom signals sent throughout Kiwi TCMS. You can connect your own
 handlers if you'd like to augment some of the default behavior!
 
 If you simply want to connect a signal handler add the following code to your
@@ -14,7 +14,7 @@
 a new Django app and connect your handler function(s) to the desired signals
 inside the
 `AppConfig.ready
-<https://docs.djangoproject.com/en/2.0/ref/applications/#django.apps.AppConfig.ready>`_
+<https://docs.djangoproject.com/en/2.2/ref/applications/#django.apps.AppConfig.ready>`_
 method. When you are done connect your Django app to the rest of Kiwi TCMS by
 altering the following setting::
 
@@ -29,6 +29,7 @@
 
     'notify_admins',
     'pre_save_clean',
+    'handle_comments_pre_delete',
     'handle_emails_post_case_save',
     'handle_emails_pre_case_delete',
     'handle_emails_post_plan_save',
@@ -158,3 +159,19 @@ def handle_emails_post_run_save(sender, *_args, **kwargs):
         subject, context = history_email_for(instance, instance.summary)
 
     mailto(template_name, subject, instance.get_notify_addrs(), context)
+
+
+def handle_comments_pre_delete(sender, **kwargs):
+    """
+        Delete comments attached to object which is about to be
+        deleted b/c django-comments' object_pk is not a FK relationship
+        and we can't rely on cascading delete!
+    """
+    from tcms.core.helpers.comments import get_comments
+
+    if kwargs.get('raw', False):
+        return
+
+    instance = kwargs['instance']
+
+    get_comments(instance).delete()

tcms/testcases/apps.py

@@ -12,3 +12,4 @@ def ready(self):
         pre_save.connect(signals.pre_save_clean, TestCase)
         post_save.connect(signals.handle_emails_post_case_save, TestCase)
         pre_delete.connect(signals.handle_emails_pre_case_delete, TestCase)
+        pre_delete.connect(signals.handle_comments_pre_delete, TestCase)

tcms/testruns/apps.py

@@ -5,9 +5,10 @@ class AppConfig(DjangoAppConfig):
     name = 'tcms.testruns'
 
     def ready(self):
-        from django.db.models.signals import post_save, pre_save
-        from .models import TestRun
+        from django.db.models.signals import post_save, pre_save, pre_delete
+        from .models import TestExecution, TestRun
         from tcms import signals
 
         post_save.connect(signals.handle_emails_post_run_save, sender=TestRun)
         pre_save.connect(signals.pre_save_clean, sender=TestRun)
+        pre_delete.connect(signals.handle_comments_pre_delete, TestExecution)